Varying Mains Water Pressure to Electric Shower Upstairs Drainage and wastage systems and plumbing help, advice and answers

[Jonny Segway]

Hi

I have an electric shower in the en-suite that takes it cold feed from a T off from the same pipe that feeds the 2 header tanks in the attic - so it must be the mains. From that is a smaller bore copper pipe of about 2.5m length to the shower. However the flow changes from 2 to 4 l/min.
What causes varying flow rate? Just low pressure? (But would think it would be constant)
Shower is struggling to deal with the varying pressure and will stop heating the water.

[stoneyboy]

Hi Jonny Segway,
Usually the mains pipe to the main water tank will be 15mm, you are saying that the pipe to the shower is smaller than this. So there is probably 2 issues flow restriction due to the pipe size and pressure reduction when the tank is filling. It's worth checking the filter on the shower as a first step.
regards, S